Voters in three Bay Area counties support BART, even if they don't ride it, and would back ballot measures boosting sales or property taxes to improve the transit system, a public opinion poll shows.

The poll, which has not been released publicly, has been circulating in BART headquarters and among insiders, including labor negotiators. It's been mentioned during the transit agency's labor dispute, which has featured a 4 1/2-day strike and a month-long contract extension and is now in the midst of a 60-day cooling-off period ordered by Gov. Jerry Brown. No negotiations are currently scheduled.

Pollsters randomly dialed 1,102 registered voters in the BART district - Alameda, Contra Costa and San Francisco counties - between April 25 and May 5. The poll has a 3.4 percent margin of error. It is important to note, however, that it was taken well before the July strike.

Still, the results are promising for the transit agency, which has said it needs to raise billions of dollars over the next 15 to 20 years to pay for its share of the $15 billion needed to buy new rail cars, build a modern train maintenance center and upgrade its aging train control system.

In recent years, polls consistently showed a lack of support for tax measures to pay for transportation and infrastructure improvements. But the most recent BART poll, by Fairbank, Maslin, Maullin, Metz & Associates, found that 72 percent of those surveyed would support an additional sales tax, while 69 percent would vote for a general obligation bond, which would increase property taxes. Both would have to capture better than two-thirds of the votes in an election to pass.

Sales tax vs. bond

The greatest support - 75 percent - was for a one-eighth of a cent sales tax, with a quarter-cent tax getting 68 percent support and a one-sixteenth of a cent tax garnering 73 percent backing. An $850 million bond received 74 percent backing, compared with 69 percent for a $1.4 billion bond and 63 percent for a $3 billion bond.

BART officials and representatives of its unions may not agree on much, but both were pleased with the results of the poll.

"That's very strong feedback on a possible ballot measure," said Alicia Trost, a BART spokeswoman. "This is the first time in years that the numbers have really showed such strong support."

BART directors have discussed the possibility of a ballot measure for a few years, but poll results found little support, so the idea languished. But since the start of the year, BART officials have repeatedly mentioned a ballot measure as a necessary part of a funding package to pay for improvements.

"They haven't decided," Trost said. "But it would certainly play a role in our shared responsibility approach."

Chris Daly, a representative for Service Employees International Union Local 1021, the transit agency's largest union, said the poll results show that BART doesn't need to squeeze money out of its employees to modernize the train system. He pointed out that even after pollsters offered the potential argument that a BART tax "will get squandered on huge salaries and pensions for BART employees," 69 percent of those questioned still said they would support a tax measure.

"BART's argument that it needs to stick it to the unions to get money to pay for improvements doesn't make sense in light of the survey," he said.

On workers and pay

The poll also included a handful of questions about BART employees and their compensation. About 71 percent thought employees should contribute to their pensions, 72 percent said they should pay part of their health insurance increases, and 78 percent believed they should have to work more than 40 hours a week before collecting overtime. But about 78 percent agreed that BART employees should "receive pay increases to keep pace with the cost of living in the Bay Area."